SEVERE Bug in mc68360 _ISR_Handler???

[Chris Johns]

Joel Sherrill wrote:
> 
> Chris could you repost it to the list.  Eric Norum and I wondered
> if the logic to enable it should be something like:
> 
> HAS_SEPARATE_STACKS==0 && COLDFIRE==0 && 060==0
> 

I also think this is the correct combination.

>
> I will then put this in the 4.5 branch, mainline, and
> in a patches directory on the ftp server.
> 

Great. A big thanks to Thomas for the analysis.

-- 
 Chris Johns, cjohns @ cybertec.com.au
-------------- next part --------------
*** rtems-4.5.0.orig/c/src/exec/score/cpu/m68k/cpu_asm.S	Fri Mar 30 12:55:35 2001
--- rtems-4.5.0/c/src/exec/score/cpu/m68k/cpu_asm.S	Wed Jul 18 23:44:51 2001
***************
*** 221,226 ****
--- 221,245 ----
          bne     exit                     | NOT outer level, so branch
  #endif
  
+ /*
+  * Check the PC on the stack to see if it is _ISR_Handler. If it
+  * is we have the case of nesting interrupts without the dispatch
+  * level being incremented. The processor places the next instruction
+  * that is to be executed when the RTE instruction is executed on the 
+  * stack. If we find we have nested without the dispatch level being
+  * incremented simply return from the exception to allow the outer
+  * to execute.
+  *
+  * The Coldfire and 68060 let the first instruction execute before
+  * processing a new higher priority interrupt so do not need to
+  * perform this test.
+  */
+         
+ #if ( M68K_HAS_SEPARATE_STACKS == 0 && M68K_COLDFIRE_ARCH == 0 && M68K_68060_ARCH == 0 )
+         cmpl    #_ISR_Handler,a7@(SAVED+PC_OFFSET)
+         beq     exit        
+ #endif
+         
          tstl    SYM (_Context_Switch_necessary)
                                           | Is thread switch necessary?
          bne     bframe                   | Yes, invoke dispatcher
***************
*** 229,235 ****
                                           | signals sent to Run_thread
                                           |   while in interrupt handler?
          beq     exit                     | No, then exit
- 
  
  bframe: clrl    SYM (_ISR_Signals_to_thread_executing)
                                           | If sent, will be processed
--- 248,253 ----